The present invention relates, in general, to electronics, and more particularly, to semiconductors, structures thereof, and methods of forming semiconductor devices.
In the past, various methods and devices were developed for acoustic measurement systems. Acoustic measurement systems were used in a wide variety of applications, including in automotive applications for detecting the distance, as well as the rate of change of distance, between the vehicle and objects in the vicinity of the vehicle, such as other vehicles or people. Some of the methods used by prior acoustic measurement systems for calibrating or adjusting the acoustic measurement system resulted in inaccurate measurements and some were especially inaccurate for short range measurements. In some example systems, the transmitted pulse duration and the decay time of the sonic transducer could result in an unusable area in which the ultrasonic sensor could not detect an object.
Some applications included a separate operation to check and/or possibly adjust the transmitter frequency. The system could not be used for detecting distances during this separate operation thereby reducing system performance. A method measuring the transducer settling time and varying the receiver center frequency in disclosed in European patent no. EP 1410950 B1. Another example may be described in an application note no. AN4398 from Maxim corporation of 160 Rio Robles, San Jose, Calif. 95134. One disadvantage of this method and other known transducer diagnostic methods based on settling time measurement is the necessity to perform the transducer diagnostic over a separate predetermined time period before the actual process of monitoring the system in order to test the freedom of the transducer from defects and separately from making a distance measurement. Such an operation could decrease system efficiency and could place an increased load on the controller.
Accordingly, it is desirable to have an acoustic measurement system including circuits and/or methods therefor that include more accurate calibration and/or adjustments that facilitate improved efficiency and/or improved accuracy.
For simplicity and clarity of the illustration(s), elements in the figures are not necessarily to scale, some of the elements may be exaggerated for illustrative purposes, and the same reference numbers in different figures denote the same elements, unless stated otherwise. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying element or current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control element or control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Additionally, one current carrying element my a carry current in one direction through a device, such as carry current entering the device, and a second current carrying element may carry current in an opposite direction through the device, such as carry current leaving the device. Although the devices are explained herein as certain N-channel or P-Channel devices, or certain N-type or P-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. One of ordinary skill in the art understands that the conductivity type refers to the mechanism through which conduction occurs such as through conduction of holes or electrons, therefore, and that conductivity type does not refer to the doping concentration but the doping type, such as P-type or N-type. It will be appreciated by those skilled in the art that the words during, while, and when as used herein relating to circuit operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay(s), such as various propagation delays, between the reaction that is initiated by the initial action. Additionally, the term while means that a certain action occurs at least within some portion of a duration of the initiating action. The use of the word approximately or substantially means that a value of an element has a parameter that is expected to be close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to at least ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are reasonable variances from the ideal goal of exactly as described. When used in reference to a state of a signal, the term “asserted” means an active state of the signal and the term “negated” means an inactive state of the signal. The actual voltage value or logic state (such as a “1” or a “0”) of the signal depends on whether positive or negative logic is used. Thus, asserted can be either a high voltage or a high logic or a low voltage or low logic depending on whether positive or negative logic is used and negated may be either a low voltage or low state or a high voltage or high logic depending on whether positive or negative logic is used. Herein, a positive logic convention is used, but those skilled in the art understand that a negative logic convention could also be used. The terms first, second, third and the like in the claims or/and in the Detailed Description of the Drawings, as used in a portion of a name of an element are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein are capable of operation in other sequences than described or illustrated herein.